Advanced Circuit driving techniques - compound corners
In this article we will be discussing Compound Corners which are common to almost every race circuit, with accomplished race driver and personal coach, Nigel Greensall. You can click on any of the screenshots to view a full size version.
Definition
Compound corner: a series of corners, close enough such that the car is always turning and never travelling in a straight line.
The following data was taken from a Funcup race at Misano in 2009:
Nigel Greensall- ‘It is a common mistake to treat compound corners as two separate items, whereas they should be tackled as one section, with sacrifices being made in the first corner to gain maximum exit speed. It often seems counter-intuitive not to maximise the speed through the first corner, but the end result is often a faster lap.
There are many examples, but let’s take Misano Circuit which is shown on the left, Turns 12 and 13 which consists of a shallow right hand corner followed by a sharper right hand corner.
On first inspection you may naturally assume that you have to clip apexes of both Turns 12 and 13 to get the best lap-time.
However, there are many other ways to take these corners and I have found that the quickest for me is to almost ignore Turn 12 by missing the apex completely, and set yourself up for a nice wide entry into Turn 13, which seems a little odd at first.
To see this line in action, have a look at the image on the left, which shows my preferred line in red, and my team mates line in blue.
The red line misses the apex of Turn 12 by almost 2m, but maintains the same apex speed of 105mph as the blue line which clips the apex.
Interestingly, through Turn 12 you are not quite on the limit of grip (a peak of 0.85G), so you can experiment with your lines through here without losing any speed.
This wider line is also slightly shorter, which also gives a small advantage.
The screenshot on the right shows the apex point of Turn 12, where both approaches have the same speed, 105mph.
It is after this point where the reason for this wider line becomes clearer.
If you treat Turn 12 as a conventional corner and clip the apex, you cannot get far enough across to use the whole width of the track into Turn 13.
By running wide in Turn 12, you can get much further over to the left for the entry into Turn 13 allowing more speed to be carried around the corner.
Using more screenshots from the in-car video, you can see just how much closer to the edge of the track (just before Turn 13) I could go, whilst carrying 7mph more speed:
If we look at the Apex speeds of the second turn using Circuit Tools software, the gain in speed is even greater:
In this screenshot you can see that the wider line allows me to carry 11mph more at the Apex, the upper graph is the speed, and the lower graph is the Delta-T or time difference between the two laps.
The analysis software showed a total gain of 0.67s in this section, which was very simple to achieve, just by taking a slightly wider line through Turn 12, which is very easy to do!’
We now zip 2700 miles across to the Dubai Autodrome in an Aston Martin GT4.
Nigel Greensall - ‘Here’s a great example of compound corner, Turn 14 (Parabolica) and Turn 15 on the Dubai Autodrome GP layout.
This is another example of where you need to think of them as a whole rather than as two separate corners.
Turn 14, the Parabolica, is slightly banked, and being a desert circuit sand tends to drift across and collect on the outsides of the track.
There is only a very short straight before Turn 15 and this is the reason why you can take an unusual line through and compromise the Turn 14 slightly to gain an overall advantage.
If you attack Turn 14 as a conventional corner, you may start off wide and sweep in for a late apex to maximize your exit speed. This is in fact the line that the race school teaches you.
This would probably work fine if there wasn’t another corner straight afterwards.
This second corner means that the exit speed of Turn 14 is not so important, because you can’t carry this extra speed down a long straight.
If there wasn't a corner straight afterwards, then you may take the conventional line to gain the maximum corner exit speed which would be carried all the way down the straight.
Because there is no long straight after Turn 14, what becomes important is getting to Turn 15 as soon as you can, so in this case it is better to take the shortest route possible and take a very tight line around the Turn 14.
This has the added advantage at this track of missing out on the sandy outer edges of the track.
This seems as though you would lose a lot of speed going round Turn 14, and indeed the wider line has an apex speed of 89km/h (55mph) compared with 79km/h (49mph) for the tighter line. Yet this line is 0.45s quicker, which is very counter-intuitive!
However, the reason this works is the really interesting part; the tighter line is 13.9m (45feet) shorter than the blue line, so even though the blue line had a higher average speed, the significantly shorter distance has a pronounced effect and in this example gives a 0.45s advantage between the entry to Turn 14 and the exit of Turn 15 and the exit speeds are almost identical.
Incidentally, the blue trace was my team mate’s fastest lap, who is an instructor at the circuit who was quite surprised when I showed him the data!
Below is the data shown in the analysis software, the lower graph is the Delta-T or continuous time difference between the two laps (using position not distance as this wouldn’t be accurate for such a situation) and the upper trace is the velocity. You can also see in the video that I am much further over towards the kerbing at this point, and also travelling 6 mph slower.’
However, at the turn in point for Turn 15 I have travelled 13.9m (45 feet) less distance than the blue path, which has given me a big advantage.'
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